1. Technical Field
Embodiments described in this disclosure generally relate to storage area networks (SAN). More particularly, the described embodiments relate to methods and apparatus for providing SCSI acceleration as a service in a SAN.
2. Description of the Related Art
Modern data centers are built around storage area networks used to provide secure, reliable, and scalable centralized data-storage facilities. A storage area network (SAN) provides a high-speed special-purpose network that interconnects different data storage devices and associated data hosts on behalf of a larger network of users. Generally, a SAN is used to attach computer storage devices, e.g., disk arrays, tape libraries and optical jukeboxes, to a host. The SAN operates such that the storage devices appear to each host as being locally attached, i.e., as though the storage devices where physically connected to the host.
Fiber Channel (FC) or Fibre Channel over IP (FCIP) is typically used to interconnect multiple data centers, e.g., to consolidate storage and physical tape libraries for disaster recovery. Typically, FC is used to interconnect the datacenters and FCIP is used to interconnect the SAN islands across the WAN using the IP cloud. Frequently, applications run across these environments provide remote replication of storage arrays and tape backups to vault the tapes in a common location. The latency introduced by MAN and WAN links and the requirements of the SCSI I/Os (especially for sequential devices such as tapes) significantly affect the performance of such applications. Accordingly, some acceleration techniques have implemented at the end points of the two sites over the MAN or WAN. As the SCSI I/Os are bidirectional in nature; however, these techniques require the traffic flows to traverse the same end points in both the directions. In the case of SCSI write acceleration, e.g., a given I/O must traverse the same end points. Similarly, in the case of tape acceleration, the entire traffic flow must traverse the same end points as this technique operators over multiple I/Os. These requirements have resulted in awkward network topologies to force certain traffic flows over the endpoint nodes connecting two SANS in order for these acceleration techniques to function.